Exploration of adverse events associated with risdiplam use: Retrospective cases from the US Food and Drug Administration Adverse Event Reporting System (FAERS) database

Risdiplam is a new drug for treating spinal muscular atrophy (SMA). However, pharmacovigilance analyses are necessary to objectively evaluate its safety—a crucial step in preventing severe adverse events (AEs). Accordingly, the primary objective of the current study was to examine the AEs associated with risdiplam use based on real-world data obtained from the US Food and Drug Administration Adverse Event Reporting System (FAERS) database. More specifically, we examined incidents reported between the third quarter of 2020 and the second quarter of 2023. The imbalance of risdiplam-related AEs was evaluated by computing the reporting odds ratio. A total of 5,406,334 reports were thoroughly reviewed. By removing duplicate reports, we identified 1588 reports in which risdiplam was the main suspected drug whose use was accompanied by 3470 associated AEs. Among the included AEs, 703 were categorized as serious and 885 as non-serious. Risdiplam use induced AEs across 18 organ systems, resulting in 130 positive signals. Notably, we detected new AE signals, including cardiac arrest, nephrolithiasis, tachycardia, loss of libido, and elevated hepatic enzyme activities; however, no ophthalmologic toxicity was reported. Although these new adverse reaction signals associated with risdiplam have been defined, long-term clinical studies are needed to confirm these findings. Nevertheless, our findings provide a valuable reference for improving the clinical management of SMA.


Introduction
Spinal muscular atrophy (SMA) is a genetic autosomal recessive disease, which means that it requires two copies of the mutated gene to be inherited.It is estimated to occur in approximately one of every 6,000-10,000 live births [1].The mutated survival motor neuron 1 (SMN1) gene, encoding SMN, is the primary factor responsible for SMA development [2].The disease is distinguished by the gradual weakening and immobility of muscles near the centre of the body and is categorized into types 1, 2, 3, and 4 [3], which align with the appearance of symptoms in the first 6 months, 7-18 months, > 18 months, and 20-30 years, respectively [4].Infants with type 1 SMA are typically unable to sit independently [5] and, if left untreated, rarely survive beyond their second year of life [5].Although individuals with type 2 SMA may be able to sit or stand with assistance, they lack the ability to walk independently.Type 3 SMA is characterized by symptoms that develop after 18 months [5], and type 4 represents a milder form that occurs in adults and does not significantly impact life expectancy [6].Meanwhile, by modifying the splicing of survival motor neuron 2 (SMN2) pre-mRNA, risdiplam upregulates SMN protein levels [4].Hence, this medication elicits clinical improvements in motor function among individuals with SMA, including children, teenagers, and adults [7].Furthermore, it has been approved for SMA treatment in various countries [6].Particularly, on 7 August 2020, the United States Food and Drug Administration (FDA) approved risdiplam as a treatment option for patients with SMA who are two months or older.
During the clinical phase III trials of risdiplam, the most frequently reported adverse events (AEs) were fever, diarrhoea, skin rash, ulcers in the mouth and oral area, urinary tract infection, and joint pain [8].According to Masson et al. [9], upper respiratory tract infection was the most frequently reported AE, affecting 22 infants (54%).However, pneumonia was the most common serious AE, occurring in 16 infants (39%), followed by respiratory distress, affecting 3 infants (7%).Clinical trials have provided information regarding the long-term effectiveness and safety of risdiplam.However, the relatively small sample size has resulted in most AEs being associated with various organs; additionally, there is a lack of extensive data on the effectiveness and safety of risdiplam.
The openly accessible US Food and Drug Administration Adverse Event Report System (FAERS) database provides information about a wide range of AEs associated with drugs that are reported by drug manufacturers, patients, and healthcare professionals [10].Indeed, its global reach has resulted in collection of information from reports from the United States as well as various other countries [10].In this study, a comprehensive risk profiling of risdiplam was conducted using information from the FAERS database to provide a valuable reference for improving the clinical management of SMA.

Data source
The data used in this study were obtained from the publicly available FAERS database.The FAERS data files contained seven datasets-patient demographics and administration (DEMO), drug details (DRUG), records of AEs (REAC), patient outcomes (OUTC), sources of reports (RPSR), start and end dates of therapy for the reported drugs (THER), and indications for drug usage (INDI) [11].To conduct this study, we extracted all data in the ASCII format, encompassing the timeframe from Q3 of 2020 to Q2 of 2023.Subsequently, we imported the data into the SAS 9.4 software for cleaning and analysis.This retrospective study analysed anonymized publicly available human data.Accordingly, the requirement for patient consent was waived, and the study was deemed exempt from ethical review by the Ethics Committee of Chongqing Youyoubaobei Women and Children's Hospital on 13 July 2023.

Data processing
Following the FDA-recommended duplicate reporting method, the DEMO files were processed by selecting and sorting them first using CASEID, then using FDA_DT, and finally using PRIMARYID.To ensure correctness, the most recent FDA_DT (date the FDA picked up the case) was selected when it matched the CASEID (FAERS case identification number) [11].In the case when CASEID and FDA_DT were identical, the report with the higher PRIMARYID (a unique identifier for FAERS reports) was chosen [11].Notably, the AEs in the FAERS are labelled using the preferred terms (PTs) from the International Dictionary of Medical Terms (MedDRA).MedDRA undergoes yearly updates in March and September and includes adjustments to the PTs and the system organ classification (SOC).Accordingly, in the present study, the latest MedDRA version (MedDRA, version 26.0) was used to correct the PTs and obtain the latest SOC and PT information from the REAC files.

Targeted drug screening
In the FAERS database, the DRUGNAME field represents the name of the drug, while the PROD_AI field represents the product composition.The PROD_AI field was added to the FAERS database in the third quarter of 2014.Regarding drugs approved for marketing after this period, the target drug can be screened based on PROD_AI.Conversely, for drugs approved before the third quarter of 2014, screening is based on DRUGNAME and PROD_AI, with reports limited to "primary suspicion (PS)."Risdiplam was approved by the FDA on 7 August 2020, making it eligible for screening via the PROD_AI field, which is indexed with "Risdiplam" as the keyword.

Statistical analysis
Analysing disproportionality involves the utilization of statistical methods to compare the reporting rates of the study drug with those of all drugs combined in the spontaneous reporting database [12].Following the principles of non-proportional analysis, the reporting odds ratio (ROR) was utilized to assess the relationships between the drugs and selected AEs [11].A sign of imbalance was identified when the minimum value of the 95% confidence interval (CI) for ROR was > 1 and it was supported by at least three pieces of evidence [10,13,14].The calculations were derived from the 2×2 contingency table (Table 1 Descriptive statistics were executed to summarize the demographic traits of the patients and clinical features retrieved from the FAERS database.A p-value < 0.05 was used to establish statistical significance, with a 95% CI applied.

General characteristics
During the study period, the FAERS database reviewed 5,406,334 reports.After excluding duplicates, we identified 1588 reports linked to risdiplam as the primarily suspected drug, along with 3470 related AEs.  2, providing details about the clinical features.Among the included reports, 703 cases were categorized as serious and 885 as non-serious.Females accounted for 47.54% of the cases.In addition, most reported cases with known ages involved individuals < 45 years of age.The USA reported the highest number of AEs, at 75.94%, followed by the UK (4.09%), the Netherlands (2.58%), India (1.95%), and Germany (1.83%).The annual number of reports showed an increasing trend from 2020 to 2023.

Time to event onset
Information regarding for the reports that included AE onset (n = 401) is provided in Table 2.
The median duration from the beginning of the events was 64 days (range: 10-333 days).The time when the AEs began is illustrated in Fig 2 .Most AEs occurred within the first month (38.9%), followed by those occurring after one year of risdiplam treatment (23.19%).

Signal detection
Fig 3 presents the proportion of AEs categorized under the SOC.AEs were most commonly observed in the general disorders and administration site conditions category (21.53%), followed by those in gastrointestinal disorders (16.46%), infections and infestations (11.67%), injury, poisoning, and procedural complications (8.04%), and nervous system disorders (5.88%).Table 3 shows the distribution of positive signals under SOC and the number of AE reports by sex, age group, and reporting country.We found that risdiplam induced AEs across 18 organ systems, resulting in the detection of 130 positive signals.Across sex and age groups, general disorders and administration site conditions, gastrointestinal disorders, and infections and infestations were among the most prevalent conditions.However, notable variations were detected among countries.Specifically, in the Netherlands, the leading three were investigations, infections and infestations, and metabolism and nutrition disorders.Table 4 lists the top five AEs regarding signal strength at the PT level by sex, age group, and reporting country that produced a positive signal.In the sex subgroup, product container issues was mentioned by males and female.In addition, dermatitis diaper, maternal exposure timing unspecified, loss of libido, and bladder pain were reported in the female group, while tracheostomy, mechanical ventilation, respiratory tract infection viral, and motor dysfunction were reported in the male group.In the age subgroups, product container issues were reported  Table 5 presents the positive signal-producing AEs at the PT level, categorized by sex, age group, and reporting country, with the top five reported events showcased.Diarrhoea was reported in the different sex and age groups.In the sex subgroups, the most frequent reports were of diarrhoea in males and asthenia in females.In the different age groups, pneumonia (age < 18 years), Asthenia (age � 18 years but less than 45 years), and diarrhoea (age � 45 years) were the most frequently reported signal-producing AEs.In the country groups,  diarrhoea (USA), lower respiratory tract infection (UK), hypokalaemia (Netherlands), death (India), and drug ineffectiveness (Germany) were the most commonly reported conditions.Table 6 presents the newly identified AEs that were reported at the PT level with a minimum occurrence of ten and a detected positive signal.The three most frequently reported events in order were asthenia, fatigue, and death.Furthermore, cardiac disorders were associated with three different AEs: increased heart rate, tachycardia, and cardiac arrest.Similarly, two AEs were associated with renal and urinary disorders: renal and urinary renal and urinary disorders.

Discussion
Maintaining a constant awareness of the potential signs of harmful drug reactions (ADRs) and consistently reporting suspected drug-related reactions after drug approval are crucial for evaluating the safety of a medication and achieving an equilibrium between its benefits and risks when making clinical decisions [15].Herein, to prevent significant drug safety issues, risdiplam-recently approved for treating SMA-was subjected to pharmacovigilance analyses to objectively evaluate its safety.We identified 130 positive AE signals related to risdiplam, involving several systems, such as general disorders and administration site conditions, gastrointestinal disorders, infections and infestations, and nervous system disorders.The AEs associated with risdiplam that were observed in previous clinical studies [1,8,9] are consistent with our findings (Tables 4 and 5) and include diarrhoea, pyrexia, vomiting, lower respiratory tract infection, urinary tract infection, and constipation.The top five most frequently reported AEs that generated positive signals varied by sex, age group, and reporting country.Diarrhoea and pneumonia were the most frequently reported AEs according to sex, age group, and reporting country.
Non-clinical studies have shown that risdiplam, which modifies the splicing of SMN2 mRNA, also affects other mRNA splice targets such as Forkhead Box M1 (FOXM1) and MAP kinase-activating death domain protein (MADD) [16][17][18].Our study revealed that females reported decreased libido, generating the fourth strongest signal, which was not reported by males.However, we did not observe other AEs that generated a favourable indication and were of significance to reproduction.In a previous study, seminiferous tubule degeneration was noted in rats, with a 50% reversal rate of germ-cell degeneration in the testes observed in rats exposed to risdiplam [16].Accordingly, it is expected that any effects on the male reproductive system caused by these SMN2 mRNA-splicing modifiers would be reversible in humans [16].Furthermore, we identified certain novel negative occurrences that resulted in positive signals, including cardiac arrest, tachycardia, urinary retention, flatulence, photosensitivity reaction, and elevated hepatic enzyme activities.Although the precise underlying mechanisms remain unclear, this discovery highlights the need for clinicians to not exclude risdiplam when considering the cause of these AEs.
Risdiplam can induce off-target effects when splicing or replacing the defective SMN 1 gene [19].These off-target effects are believed to be responsible for AEs [19] and may involve misidentification and non-specific recognition.While risdiplam primarily impacts SMN2 exon 7 to treat SMA, it can also affect MBNL1 (muscleblind-like 1) exon 5, DST (i.e., BPAG1, bullous pemphigoid antigen 1), TEAD1 (transcriptional enhancer activator domain 1), and THOC5 (THO complex 5).Hence, the off-target effects of risdiplam can lead to recognition errors, as these impacted exons have structures similar to those of their intended targets.For example, MBNL1 exon 5 has a G residue in its last position, as do DST, TEAD1, and THOC5 [20].MBNL1 plays a crucial role in controlling RNA metabolism; MBNL1 exon 5 encodes a signal that determines the location of MBNL1 in the cytoplasm and is necessary for general gene expression regulation [21].Meanwhile, abnormal transcripts that contain repetitive sequences and trap MBNL1 in the cell nucleus have been linked to ankylosing muscular dystrophy [22].DST, TEAD1, and THOC5 encode proteins involved in microtubule organization, transcription, and RNA metabolism, respectively.Accordingly, disruption of their expression or function is associated with neurological disorders [23].Additionally, we observed negative effects within specific organs, including muscle weakness, myalgia, muscle twitching, and paraesthesia.Therefore, clinicians must consider these potential AEs when considering the use of risdiplam.In addition to its non-target effects on the disease targets FOXM1 and MADD [24], risperdal also targets the 5 0 -splice site and GA-rich sequence, located 24 nucleotides upstream, for SMA treatment [25].FOXM1 encodes a crucial regulator of the cell cycle.That is, FOXM1 is necessary for cell division and is predominantly located within rapidly dividing cells, such as those in the gastrointestinal tract, male germ cells, skin, and haematopoietic progenitors in the bone marrow.Additionally, MADD is associated with apoptosis.These observations indicate that risperdal, a non-specific drug, targets FOXM1 and MADD, thereby disrupting the cell cycle, inducing micronucleus formation, and initiating apoptosis [24].Witte et al. [26] showed that drugs modifying SMN2 splicing produce off-target effects, including thrombotic microangiopathy, which can cause albuminuria and haematuria.Moreover, Qi et al. [27] noted a potential correlation between FOXMl targets and albuminuria, which is consistent with the urinary conditions detected in the current study, such as urinary retention, Nephrolithiasis.It is, thus, necessary to closely monitor urinary system functioning in patients with renal conditions prescribed risdiplam and consider potential dosage adjustment.Moreover, additional analysis regarding the safety and efficacy of risdiplam use for patients with renal impairment is warranted.Wu et al. [28] proposed a potential association between MADD and increased vulnerability to diastolic heart failure.They argue that MADD is crucial in balancing the effects of TNF- [29].The immediate effect on action potential duration, peak Ca 2+ transient amplitude, and the rate of Ca 2+ decline is detectable with low levels of TNF-, varying between 200 and 500 U/ mL [28].In the present study, we identified safety signals related to tachycardia, cardiac arrest, and prolonged QT.These findings indicate that it is essential to monitor cardiac function during clinical use and consider potential dose adjustment.Although long-term, nonclinical safety studies in monkeys revealed off-target retinal effects [30], Robert et al. [31] verified that risdiplam does not harm the eyes of children or adults.However, notably, the label for risdiplam mentions the presence of retinal toxicity observed in animal studies, the specific mechanisms for which remain unclear.
Furthermore, we found that the signal intensity and frequency of AEs related to product leakage, product container issues, and product container seal problems were relatively high.This may be due to negligence in the usage of risdiplam and management of its dosage.This highlights the need for improved education and standard management of risdiplam use to prevent AEs resulting from product misuse.In addition, the patients reporting these AEs primarily included children under 18 years of age, the main incidence group being infants within 18 months of birth.Accordingly, healthcare professionals must closely monitor children prescribed this drug for potentially severe AEs.

Conclusion
Through a comprehensive analysis of reports from the FAERS database, we demonstrated the potential risk signal and timing of AEs associated with risdiplam use.Major AEs, such as tachycardia, cardiac arrest, and nephrolithiasis, may occur; however, no cases of ophthalmologic toxicity were reported.Hence, clinicians must remain cautious regarding the potential occurrence of serious AEs associated with risdiplam, such as cardiac arrest, loss of libido, and elevated hepatic enzyme activities.Moreover, patients must be properly educated about potential AEs, and their physical well-being must be monitored to optimize their quality of life.These steps contribute to effective disease management.However, long-term clinical studies are needed to confirm our findings concerning the AEs associated with risdiplam use.
Fig 1 demonstrates the steps involved in reviewing the reports.Risdiplam-related reports are listed in Table

Table 2 . Clinical characteristics of the included cases treated with risdiplam and the associated adverse events.
in all groups < 65 years of age.Meanwhile, kidney stones were reported in two groupsage < 18 years and age � 45 years but less than 65 years.Among the different age groups, the greatest AE signal intensities were assigned to bronchial obstruction (age < 18), product container issues (age � 18 years but less than 65 years), and diarrhoea (age � 65 years).

Table 4 .
(Continued) Age � 65 years and adverse events reported in the Netherlands, India, and Germany yielded fewer than five positive signals, summarized according to the actual situation.

Table 5 . Five most frequent adverse events that generated positive signals at the PT level based on subgroup analyses according to sex, age, and reporting country.
Note: Age � 65 years and adverse events reported in the Netherlands, India, and Germany yielded fewer than five positive signals, summarized according to the actual situation. https://doi.org/10.1371/journal.pone.0298609.t005